Meanwhile an increase in the share of private funding, for example from chemical or machinery companies, has not filled the gap, he says.

While there are other factors that have affected food production, including climate change and climate variability, Mullen says his own research show a direct link between agricultural r&d and productivity growth.

"We are now observing a decline in productivity of growth that could be caused by the decline in research investment," he says.

And he says every year that expenditure declines will have an impact on productivity down the line.

"A decline in expenditure this year in r&d will have an impact on productivity five or 10 years down the track, and that might have an impact for another 30 or 40 years."

Mullen says Australia should halt the fall in agricultural r&d to ensure farmers will have the knowledge and technologies they need to farm sustainably and cope with climate change.

Bang for the buck

According to Mullen, public funding for agricultural research by Commonwealth and state institutions has declined from 75% in the early 1990s to 60% in 2003, as a share of total expenditure.

And some people are questioning how the remaining dollars are being spent.

In recent years Australia's national research agency CSIRO has made a deliberate shift away from what it terms "incremental agricultural research" on farms.

Dr Michael Borgas of the CSIRO Staff Association says CSIRO is focusing more on "trendy breakthrough science" based in laboratories, such as molecular biology and information systems.

He says while lab-based research can be done from centralised locations, such as Canberra, it removes scientists from day-to-day contact with the real world problems that farmers are facing.

This partnership between scientists and farmers in on-farm research has traditionally provided major breakthroughs in productivity, says Borgas.

"It's necessary for the scientist to get the practical on-farm knowledge to learn really what the questions are that the science needs to answer, and you can't do it in an abstract way just sitting in a laboratory," he says.